1. Technical Field
The present invention relates to lighting devices, and a power supply system for a lighting device.
2. Description of Related Art
Currently, various solar cell panels are designed to receive and convert sunlight energy into electrical energy, thereby powering various electronic devices, such as lighting devices. Such solar cell panels have been applied on roofs of buildings and cars, and on surfaces of portable electronic devices.
A typical solar cell panel includes a P-type semiconductor layer and an N-type semiconductor layer. When sunlight falls on a surface of the P-type semiconductor layer or on a surface of the N-type semiconductor layer, a part of the sunlight is unavoidably reflected by the surface, and the remainder is absorbed by the corresponding P-type semiconductor layer or N-type semiconductor layer. Photons in the absorbed sunlight collide with electrons in the corresponding P-type semiconductor layer or N-type semiconductor layer. Thereby, electron-hole pairs are generated, and thus an electric field is formed between the P-type semiconductor layer and the N-type semiconductor layer. In this way, the solar cell converts the sunlight energy into electrical power.
The solar energy that the solar cell panel receives is limited by the surface area exposed to sunlight. Buildings, cars and portable electronic devices have finite outside surface areas. Accordingly, a large surface area for laying out a large solar cell panel or a plurality of solar cell panels may be unavailable.
What are needed, therefore, are a power supply system and a lighting device using the power supply system, which can overcome the above shortcomings.